Anode Cathodic Protection Research Articles

Characterization of Al-Zn-Sn as Sacrificial Anodes to Protect Underground Oil Pipelines in Al-Hilla Regional

Sacrificial anode cathodic protection is one of the most widely used methods in protecting buried oil pipe lines against the corrosion damages. In the present work, a series of Aluminum alloys have been prepared as sacrificial anodes candidates to be used in the protection of the oil pipelines that pass through the Al-Hilla region. These prepared alloys were microstructurally and electrochemically characterized to evaluate their performance as Al-sacrificial anodes for cathodic protection of oil pipes The relationships between the protection potential with time, sacrificial anode life, discharge currents, and capacity of sacrificial anodes were found, taking into consideration the distance between sacrificial anode and protected steel sample. According to the results obtained, the best selection of sacrificial anodes was (Al-4% Zn-0.5% Sn) alloy at 30cm in Al-Hilla region.

The selection and use of cathodic protection systems for the repair of reinforced concrete structures

Cathodic protection (CP) is an electrochemical repair technique that has increasingly been used for the repair of reinforced concrete structures in the UK and worldwide. Cathodic protection generally works by the passing of a small electrical current from the anode to the corroding steel reinforcement thereby protecting it from further deterioration by increasing the hydroxyl ions locally. This paper has looked at the advantages and disadvantages of using the two types of cathodic protection systems, namely sacrificial anode and impressed current CP, and highlighted some of the design considerations and challenges faced on a number of case histories that Mouchel have undertaken. From our experience the decision whether to use an impressed current CP system or a sacrificial anode CP system is influenced by a number of factors including but not limited to the condition (the level and extent of deterioration) of the structure, the client’s budget and the anticipated life expectancy of the structure following the repairs. Experience at Mouchel indicates that the circumstances where SACP is most suitable includes small and targeted repairs, repairs where budget costs are limited and repairs where the life expectancy is anticipated to be around 10years. On the other hand, ICCP is generally used to address significant corrosion problems to large structures and surface areas, where life expectancy is expected to be more than 25years and where access and traffic management are challenging and very costly.

Effects of Tin on Aluminum – Zinc Alloy as Sacrificial Anode to Protect Underground Oil Pipeline in Al-Mahawil Regional

Abstract Sacrificial anode cathodic protection is one of the most widely used methods in protecting buried oil pipe lines against the corrosion damages. In the present work, a series of Aluminum alloys have been prepared as sacrificial anodes candidates to be used in the protection of the oil pipelines that pass through the Al-Mahawil region. These prepared alloys were microstructurally and electrochemically characterized to evaluate their performance as Al-sacrificial anodes for cathodic protection of oil pipes The relationships between the protection potential with time, sacrificial anode life, discharge currents, and capacity of sacrificial anodes were found, taking into consideration the distance between sacrificial anode and protected steel sample. According to the results obtained, the best selection of sacrificial anodes was Al-4% Zn-0.4% Sn) alloy at 30cm in Al-Mahawil region.

Effect of cyclic hydrostatic pressure on the sacrificial anode cathodic protection

PurposeThe purpose of this paper is to study the effect of cyclic hydrostatic pressure on the protective performance of cathodic protection (CP) system consisting of Zn‐Bi sacrificial anode and Ni‐Cr‐Mo‐V steel.Design/methodology/approachThe anode and cathode polarization curves of the driving potential and current for CP were investigated in case of cyclic hydrostatic pressure (0‐3.5 MPa) and compared with that at atmospheric pressure. The morphologies of the anode material with and without corrosion products were observed by scanning electron microscopy.FindingsThe experimental results revealed that the cyclic hydrostatic pressure had significant influence on the CP system. The anode potential instantaneously responded to the cyclic hydrostatic pressure and the discharge performance decreased due to the deposition of corrosion product. Also, the CP system exhibited higher slope parameter under cyclic hydrostatic pressure, indicating that the CP system cannot provide adequate protection for Ni‐Cr‐Mo‐V steel.Originality/valueThe results presented in this paper clearly show the effect of cyclic hydrostatic pressure on the sacrificial anode CP system, and present a foundation for further research on the practical application of sacrificial anode under cyclic hydrostatic pressure environment.

Utility of Submerged Anodes for Cathodic Protection of Above-Waterline Reinforced Concrete Elements—Part 2: Bulk Magnesium Anodes

Abstract In a previous paper (Part I), the utility of Zn-submerged bulk anodes (ZnSBA) for providing cathodic protection to the above-waterline portion of a marine-reinforced concrete bridge substructure was investigated. It was determined that polarizations greater than 100 mV reached to the top of cast-in place footers (about one meter above mean tide) but decayed sharply in the columns above this. As such, it was concluded that these anodes alone did provide some protection in the splash zone, albeit not as much as when combined with either zinc thermal-spray or zincjackets. In the present investigation, similar field trials were performed using Mg-submerged bulk anodes (MgSBA), which were considered to be potentially more effective in providing protection to the above-waterline zone because of greater driving voltage. Results of these trials indicate that 100 mV depolarization was achieved in some cases to as high as 2.5 m above mean water. In addition, the substructure footer and column with MgSBA wa...

Low Driving Voltage Aluminum Alloy Anode for Cathodic Protection of High Strength Steel

The present work was focus on developing low driving voltage sacrificial anode for high strength steels. Taking the zinc and bismuth as main active elements, we designed and prepared several aluminum alloy anodes and investigated their electrochemical performance by galvanic test in natural seawater. The results showed that the anode exhibits high performance with 0.55wt.% Zn and 0.5wt.% Bi as the alloying elements. Its potential is varied from -800mV to -820mV, the current capacity is 2565 Ahr/kg, and the dissolution is homogeneous. We concluded that Al-0.55%Zn-0.5%Bi alloy anode can be used to high strength steel for corrosion protection. The microstructures of the anodes were observed by optical microscope, the result proposed that the uniform dissolution morphology of Al-0.55%Zn-0.5%Bi anode is due to its fine grain size.

Utility of Submerged Anodes for Cathodic Protection of Above-Waterline Reinforced Concrete Elements—Part 1: Bulk Zinc Anodes

Utility of Submerged Anodes for Cathodic Protection of Above-Waterline Reinforced Concrete Elements—Part 1: Bulk Zinc Anodes

Effect of manganese addition on anode characteristics of electrolytic magnesium

PurposeThe purpose of this paper is to investigate the influence of manganese addition on sacrificial anode characteristics of electrolytic magnesium.Design/methodology/approachDifferent contents of manganese were added to magnesium. Anode characteristics were evaluated and correlated to added manganese.FindingsThe performance of an anode depends strongly on the manganese content. An optimum value for the manganese to be added was identified. The impurity levels to obtain efficiencies above 50 per cent also are reported.Originality/valueThis paper highlights the properties of magnesium‐manganese binary alloys for use as sacrificial anodes in cathodic protection.

Electrochemical Evaluation of Zn-22 wt.% Al- x wt.% Ag (x = 2, 4, 6) Sacrificial Anodes

The object of the present work was to determine the possibility that Zn-Al eutectoid alloys (Zn-22 wt.% Al), with silver contents of 2, 4 and 6 wt.%, could be used as sacrificial anodes for cathodic protection of steel structures in two test aqueous solutions: substitute ocean water and 0.5 M NaCl. Besides the as-cast condition, some samples were homogenized at 350 oC during 96 h and air-cooled. A short-term electrochemical test, DNV RP B401, as well as electrochemical impedance spectroscopy were performed to obtain electrochemical behavior and electrochemical capacity of the anodes, and to reveal any tendencies to passivation. The experimental results suggest that the Zn-Al-Ag sacrificial anodes, with both microstructures, showed a passive behavior in substitute ocean water. However, these alloys exhibited adequate potentials and electrochemical capacities to work as sacrificial anodes in 0.5 M NaCl.

EVALUATION OF THE SACRIFICIAL ANODE CATHODIC PROTECTION OF CARBON STEEL IN 0.5M NACL USING EXPERIMENTAL DESIGN

This study examined the effect of Temperature (T); flow rate(F); and pH ; on the zinc consumption as sacrificial anode in cathodic protection of steel pipe carrying saline solution (i.e., 0.5 M NaCl) using a 23 factorial design. Rates of zinc consumption during cathodic protection were measured by weight loss technique and it ranges from 7.5x10-3 to 98.9x10-3 g/cm2.day. For the system under investigation, the cell responsible for cathodic protection is Zn/NaCl/Fe .It was found that both temperature and flow rate increases the zinc consumption while pH decreases it sharply.It was found also that the interaction between the temperature and pH is the dominant term compared with other interactions.

Effect of Mg Content on the Performance of Al-Zn-Mg Sacrificial Anodes

Aluminum sacrificial anodes are widely used in cathodic protection of steel structures in sea water. In the present work, samples of Al-5.3 at.% Zn-x at.% Mg (x = 5.5-8.5) alloys were microstructurally and electrochemically characterized to evaluate their performance as Al-sacrificial anodes for cathodic protection of structures exposed to marine environments. The experiments focussed on the influence of Mg content on electrochemical behavior and efficiency. Mg was used in different concentrations ranging from 5.5 to 8.5 at.%. Short-term electrochemical tests, DNV RP B401, as well as polarization curves and electrochemical impedance spectroscopy were performed to obtain electrochemical behavior and efficiency and to reveal any tendencies to passivation. It is shown that by increasing Mg content an improvement of electrochemical properties of Al-alloy such as current capacity and then electrochemical efficiency can be obtained.

Development of high performance aluminium alloy sacrificial anodes reinforced with metal oxides

Metal composites of alumina and zinc oxide were incorporated into Al + 5% Zn alloy and the reinforced alloys were used as efficient sacrificial anodes for cathodic protection of steel objects. ZnO was not only used to reinforce the alloy matrix and improve the metallurgical characteristics but also to yield effective activation of the sacrificial anodes. Galvanic efficiency as high as 83% was achieved when 0.5% ZnO was incorporated into the anode matrix. High and steady negative potential, very low polarization and substantial reduction in self-corrosion of the anodes were observed during prolonged galvanic exposure tests. However, the incorporation of alumina into the anode matrix led to an adverse effect.

Comportamiento de ánodos de sacrificio en la protección de aluminio NV-5083 en agua de mar, bahía de Valparaíso

The behavior of aluminum and zinc alloys were evaluated and compared as sacrifice anodes in cathodic protection of aluminum NV-5083 hulls in seawater in Valparaiso bay. Samples of the aluminum alloy used to manufacture boat hulls and Al-Zn-In, Al-Zn-Sn, and Zn anodes were made. Electrochemical behavior was evaluated by means of polarization curves and corrosion potential as function of time. In parallel, galvanized pairs (boat hull-sacriice anode), were designed and immersed in the electrolyte for 16 days, determining the weight loss and evolution of the open circuit potential for each material. The results show that the aluminum based anodes provide the NV-5083 aluminum hull cathodic protection in seawater. However, they do not exceed the economical horizon and useful life of zinc anodes, because the aluminum based anodes present higher corrosion for the protection of a similar exposed area of aluminum.

A sacrificial anode retrofit program for existing cast‐iron distribution water mains

Public water utilities face a significant economic burden created by the deterioration of their water distribution systems. Applying cathodic protection (CP) can extend the life of an existing water distribution main system. This report discusses how, in 2003, the Des Moines (Iowa) Water Works (DMWW) implemented an in situ sacrificial anode retrofit program to reduce main breaks and extend the life of its system. The results of a 2003‐2004 pilot program show that a 20‐year life extension can be achieved at less than 10% of the replacement cost of the piping. Implementation of a full‐scale program should prove to be a viable economic alternative to either repairs or water main replacements in the coming years. A CP anode installation technique is discussed and economic analysis of CP versus main replacement/main break repairs is given.

Solidification of chill-cast Al-Zn-Mg alloys to be used as sacrificial anodes

In the present research, Al-Zn-Mg alloys were vacuum induction melted and gravity cast into steel molds. Ingots were microstructurally and electrochemically characterized to evaluate their performance as Al-sacrificial anodes for cathodic protection of structures exposed to marine environments. The microstructure observed in as-cast ingots consisted mainly of α-Al dendrites with 0.68 to 2.25 vol pct of τ phase in α-Al matrix and eutectic in interdendritic regions. After heat treatment, the presence of the τ phase increased up to 5 vol pct. Electrochemical efficiencies obtained in Al alloys showed maximum values of 73 and 87 pct in as-cast ingots and heat-treated ingots, respectively. In order to contribute to the development of Al-Zn-Mg anodes, the Al-5.3 at. pct Zn-6.2 at. pct Mg (Al-12 wt pct Zn-5.4 wt pct Mg) alloy was monitored to identify the temperature changes as it cools through phase transformation intervals. Growth temperatures of the phases present in this alloy were employed to predict the structure growing at fixed growth velocity. Predictions of variation of solute concentration with growth velocity in α-Al dendrites were included, too. The results of these analyses help to select alloy composition and to control microstructure in order to develop a new generation of Al-sacrificial anodes free of In and Hg.

Effectiveness of a conductive cementitious mortar anode for cathodic protection of steel in concrete

The paper reports a study on the behaviour of a cementitious conductive overlay anode used for cathodic protection (CP) of steel in concrete. The anode is made of nickel-coated carbon fibres in a cementitious mortar. Tests were carried out on concrete specimens with two layers of rebars that simulated reinforced concrete slabs. Anodic current densities in the range 10–100 mA/m2 with respect to the anode surface were imposed. Steel and anode potentials, as well as feeding voltage, were monitored. Four-hour decay and the distribution of current and potential were regularly measured. Galvanostatic polarisation tests were also carried out on the anode material immersed in saturated calcium hydroxide solutions. The maximum anode current output was evaluated. The effectiveness of patch repair of the anode, on areas damaged by excessive current output, is also discussed.

Electrochemical investigations of conductive coatings applied as anodes in cathodic protection of reinforced concrete

Results of electrochemical measurements of conductive coatings, based on the mixing of pigmentary graphite in a polymer matrix are presented in this work. Electrochemical parameters are determined for the investigated coatings during long-term anodic polarisation on reinforced concrete. Based on impedance measurements the electrochemical parameters of conducting coatings are calculated. It is shown that the investigated coatings can be used in cathodic protection of reinforced concrete. The investigations show that the optimum graphite contents in coatings used for protection of concrete should be in the range from 40% to 45%.

Conducting coatings as anodes in cathodic protection

The results have been presented of electrochemical measurements of conducting coatings, based on the mixing of pigmentary carbon in a coating polymer matrix. On the basis of impedance measurements electrochemical parameters of conducting coatings have been calculated. Simultaneously electric and electrochemical parameters have been determined of investigated coatings during long-term anodic polarisation. The results were subjected to statistical analysis and the scatter level of the experimental results was determined. It has been shown that investigated coatings can be used in cathodic protection of objects whilst maintaining assigned electric and electrochemical parameters.

Galvanic Dissolution Behavior of Magnesium-1 mass%manganese-0.5 mass%calcium Alloy Anode for Cathodic Protection in Fresh Water

Magnesium-1 mass%manganese-0.5 mass%calcium (Mg-1 mass%Mn-0.5 mass%Ca) alloy was used as sacrificial anode. This work was performed to investigate the galvanic dissolution behavior of the alloy anode for cathodic protection in fresh water. The microstructure and dissolved surface of the alloy anode were analyzed with an electron probe micro analyzer, a scanning electron microscope with energy dispersive X-ray spectrometer and a microscope. The current efficiency of the anode has been measured by laboratory test method of galvanic anodes for cathodic protection. It was found that calcium is present uniformly at the grain boundaries as Mg 2 Ca or Mg-Ca-Si compounds. Calcium compounds dissolve preferentially compared to the matrix of magnesium, as a result the anode uniformly dissolve compared to Mg-1 mass%Mn alloy anode. The current efficiency of the anode for the dissolution was higher than that of Mg-1 mass%Mn anode. On the other hand, manganese is added in order to decrease the local cathode to magnesium alloys, however the part of manganese compounds act as the local cathode in the alloys.

Conducting composites as cable anodes in cathodic protection: a literature summary

The basic characteristics of a cathodic protection system, using cable anodes, have been reviewed. Cable anodes differ from typical anode systems because of the anode installation method. An anode system based on cable anodes is not installed in point locations; the anode is located at a small distance from the protected structure and runs in parallel along the route of the structure to be protected. An elastic conducting composite of very good mechanical properties is used as the anode material. This solution can result in a reduction in operating costs, and the avoidance of under‐protected and over‐protected zones, or protective current interference, on other structures.